Eddy current inspection is commonly used as non-destructive control to detect flaws in surfaces of manufactured components fabricated from a conductive material, such as bars, tubes, and special parts for the automotive, aeronautic or energy industries.
Since the 1950's, eddy current instruments render test information on an impedance plane display. The original concept of the impedance plane display was to divide the detector coil impedance into resistive and reactive components to produce bi-dimensional figures yielding significant information on the inspected component. The concept quickly evolved as users understood the value of manipulating the impedance plane to highlight specific features of the component to be tested.
Portable eddy current instruments now offer many controls to achieve these impedance plane manipulations, including: gain, rotation, horizontal position, vertical position, horizontal gain and vertical gain. All controls are typically accessible in various instrument menus and are iteratively applied by the instrument user to produce the desired impedance plane setup. This operation can become time consuming as the user needs to go through the whole sequence before each new inspection procedure (sometimes twice for a dual frequency setup). Thus, there is a need for an easier and faster way to manipulate the impedance plane on NDT equipment, such as a portable eddy current instrument.
Another limitation of the current method is the troublesome interaction between some parameters such as vertical gain and rotation, which require some additional care when instruments settings are defined.
More specifically, some additional drawbacks involved in a typical prior art portable eddy current instrument featuring an eddy current impedance plane that shows signal produced by scanning a defect with a probe and the controls available for manipulating this impedance plane signal to enhance the detectability of defect signal over noise signal, are as follows. These controls typically involve the use of multiple buttons associated with multiple parameters displayed on the instrument screen. Parameters found on most eddy current instruments include impedance plane rotation angle, gain, horizontal gain, vertical gain and settings to configure the horizontal and vertical position of the null point. The parameters for impedance plane manipulation are sometimes located in various sub-menus of the instrument. The values for each parameter are typically modified with a knob or by using a keypad.
An inspection procedure typically describes the desirable signal shapes on a reference block in order to obtain a reliable and repeatable inspection. Those procedures typically require setting the noise signal on the horizontal axis and defines the other parameters to maximize the detectability of defect signal on the vertical axis in order to decouple the defect and noise signals. Furthermore, since eddy current parameters are closely related to probe selection, inspection condition and target defects, those parameters must be set before any inspection task.
The original impedance plane signal is iteratively modified to highlight the defect signal with the prior art method. Consecutive steps typically include gain adjustment, signal rotation, vertical gain adjustment, vertical movement of the null point and horizontal movement 14 of the null point. Those operations are often conducted on live data (in this case the user needs to repeatedly scan the defect area) or on paused (frozen) data. In the latter case, some post processing is used to manipulate the data previously acquired to reflect in real time changes made on the original signal. For purposes of illustration, the figures and descriptions provided herein are more oriented toward frozen data style manipulation.
Multi-point touch screen displays now available on the market make it possible for users to directly interface with instruments without going through menus and sub-menus. This invention provide means to benefit from a multi-point touch screen to provide new ways to manipulate an impedance plane and to circumvent current limitations of prior art methods.
An object of the invention is to reduce the number of steps required for the controls so as to produce an equivalent end result and thus to increase productivity.
Another object is to provide a simplified and more intuitive operation which, in turn, provides an enhanced user experience.